Diagnostic tests frequently require separation of a patient's whole blood sample into components, especially cellular portions from non-cellular portions e.g. serum or plasma from cells. For instance, plasma is obtained from anticoagulated blood and still contains all of the coagulation proteins, whereas serum is obtained from clotted blood with the bulk of the coagulation proteins being retained with the clot and red blood cells. Samples of whole blood are typically collected by venipuncture through a special cannula or needle attached to a syringe or an evacuated collection tube. The sample of blood in the form that is to be separated into components is typically drawn, using a needle, through a penetrable self-sealing elastomeric closure or other stopper into an evacuated tube or vial. Separation is then accomplished e.g. by rotation of the tube or vial in a conventional centrifuge e.g. a swinging bucket or a fixed angle centrifuge, or in an axial centrifuge as the different components of the whole blood have different densities.
The separated blood components normally must be removed from the stoppered vial prior to any tests being carried out on the blood component. Removal of the stopper from the vial could result in contamination of the sample and in particular could be hazardous to the person removing the stopper e.g. through contact with the blood component. Dispensing devices for removal of blood components or samples thereof are known e.g. as disclosed in U.S. Pat. Nos. 4,811,866 and 4,925,065 of T. L. Golias, published European patent application 0,348,116, also of T. L. Golias, and U.S. Pat. No. 5,030,341 of J. A. McEwen et al.
A more versatile dispensing pipette with important safety features has now been found.